The purpose of this study is to analyse the development of two apprentices' adaptive expertise in fingerprint examination across a two-year training program. The apprentices were selected from a large number of candidates to be trained at the Forensic Laboratory of the Finnish National Bureau of Investigation. The problem addressed was how the newcomers' professional vision needed for examining fingerprints developed, what kinds of agentic efforts for improving performance did they engage in when analysing successively more challenging fingerprints, and how did they themselves reflect on their developing professional performance. The study relied on multiple bodies of data consisting of a large number of fingerprints examined by the apprentices, repeated interviews, and their extensive learning diaries. The analysis revealed various challenges and obstacles of acquiring the professional vision and skills of fingerprint examination, such as identifying relevant minutiae in poor-quality fingerprints, carrying out searches through the Automatic Fingerprint Identification System (AFIS), and interpreting results. Although the apprentices cultivated self-reflective competencies, the professional practices appropriated also mirrored some of the maladaptive working habits of the experienced examiners with whom they were working. Through the training process, both of the apprentices gained professional competencies comparable with those of experienced examiners. The apprentices' ways of reflecting on their evolving professional performance differed, and there was no straightforward relation between their self-reflections and levels of performance.